It has been an ongoing debate in the tennis world - does the current 'golden era' for the game feature a 'Big Three' or a 'Big Four' including Andy Murray?

Some have argued that there is simply a 'Big Three' of Roger Federer, Rafa Nadal and Novak Djokovic, given that Murray has yet to win a grand slam tournament.

Others have hedged their bets, suggesting a 'Big Three Plus One' given the distance Murray has set between himself and the rest of the ATP Tour.

But after the Briton's heroic battle in defeat to Federer in the Wimbledon final and then his Olympic final triumph over the Swiss world number one, the question is being asked again.

Talking about the 'golden era' the game is currently going through, five-times grand slam singles champion Djokovic casually referred to a leading four.

"You have four players who are I think winning 90 per cent of all the major tournaments that you have on the tour," Djokovic told reporters on Tuesday while preparing for his opening match at this week's Cincinnati Open.

"I mean, so many titles and so much competition going on and so many great rivalries, great matches, history and all these things that are, I think, making this era a golden era."

But does that make for a 'Big Four'?

Djokovic seems to think so.

"There were different kinds of talk with the rivalries between Roger and Rafa, between me and Rafa, me and Roger, and then Andy. So there is really no story that I can say, 'Okay, that's the right one'," the Serb said of the debate.

"Andy was always part of that group of the top players. For about the last four, five years he's been in top four in the world. Now he has won Olympic Games. He's played couple of grand slam finals, so he deserves to be up there."

DRAINING DEFEAT

After breaking down in tears following his draining defeat in the Wimbledon final, Murray rode the wave of British Olympic success by getting his revenge over the Swiss by winning the gold medal game.

Djokovic said he was impressed by how Murray had coped with an emotional and high-pressure summer at home.

"It was definitely impressive performance from him at Wimbledon and at the Olympic Games even more," the Serb said.

"He always has pressure when he plays in London, in Britain. It's huge pressure on him. But I guess he's going to agree ... that over the years you get that necessary experience to know how to cope with that certain pressure.

"It's part of your life. It's part of your sport. It's something that drives you as well; that gets you to the certain level of intensity that is, I think, necessary for you to have in order to perform your best on the major tournaments."

Murray and Djokovic, who clinched the Toronto Open on Sunday, have been drawn in the same half of the draw at this week's Cincinnati Open.

Djokovic will face Italian Andreas Seppi in his opening match on Wednesday while Murray is up against American Sam Querrey who beat Austrian Juergen Melzer 4-6 6-2 6-4 on Tuesday.

Murray is the defending champion at Cincinnati, having beaten Djokovic in last year's final when the Serb retired hurt in the second set.